A ball is thrown at an angle of to the ground. If the ball lands 90 m away, what was the initial speed of the ball?

Physics

1 answer:

andre [41]3 years ago

8 0

Answer:

The initial speed of the ball is 30 m/s.

Explanation:

It can be assumed that the ball is thrown at an angle of 45 degrees to the ground. The ball lands 90 m away. We need to find the initial speed of the ball. We know that the horizontal distance covered by the projectile is called its range. It is given by :

$R=\dfrac{u^2\ sin2\theta}{g}$

u is the initial speed of the ball.

$v=\sqrt{\dfrac{Rg}{sin2\theta}}$

$v=\sqrt{\dfrac{90\times 9.8}{sin2(45)}}$

v = 29.69 m/s

v = 30 m/s

So, the initial speed of the ball is 30 m/s. Hence, this is the required solution.

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When the ions are inside the container, they are subjected to two forces, with directions opposite to each other:

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The ions will move straight and undeflected if the two forces are equal and opposite. By using Fleming Left Hand rule, we notice that the magnetic force on the (negative) ions point upward: this means that the electric field must be also upward (so that the electric force on the ions is downward). Then, the two forces are balanced if

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which translates into

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Therefore, if the speed of the ions is equal to this ratio, the ions will go undeflected.

We can even calculate the value of E at which this occurs. In fact, we know that the ions are earlier accelerated by a potential difference $V=-3000 V$ , so we have that their kinetic energy is given by the change in electric potential energy: